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UNIT 8
Chapter 8
From DNA to Proteins
UNIT 3: INTRODUCING BIOLOGY
Chapter 8: From DNA to Proteins
I. Identifying DNA as the Genetic Material (8.1)
A. Griffith finds a “transforming principle”
1. Griffith experimented with the
bacteria that cause pneumonia.
Pneumococcus bacteria
2. He used two forms and injected them into mice
a. The S, or smooth form (deadly)
b. R form, or rough (not deadly).
3. S form of bacteria killed with heat mice
unaffected
4. Injected mice with combination of heat-killed
and live R bacteria
a. Mice died
b. Griffith concluded that a transforming
material passed from dead S bacteria to live
R bacteria, making them deadly.
B. Avery identifies DNA as the transforming
principle
1. Experimented with R bacteria and extract
made from S bacteria
2. Allowed them to observe transformation of
R bacteria
3. Developed process to
purify their extract
a. Performed series of tests to find out if
transforming principle was DNA or protein
b. Performed
chemical tests that
showed no proteins
were present.
c. Test revealed that
DNA was present
4. Performed tests with Enzymes
a. Added enzymes to break down proteinstransformation still occurred.
b. Added enzymes to break down RNAtransformation still occurred.
c. Added enzymes to break
down DNA- transformation
failed to occur.
d. Concluded DNA was
transforming factor
C. Hershey and Chase confirm that DNA is the
genetic material
1. Alfred Hershey and Martha Chase provided
conclusive evidence that DNA was the
genetic material in 1952
2. Studied viruses that infect bacteria
(bacteriophage)
a. Bacteriophage is simple- protein coat
surrounding DNA core
1). Proteins contain sulfur buy very little
phosphorus
2). DNA contains phosphorus and very
little sulfur
b. Experiment No.1- Bacteria infected with phages
with radioactive sulfur atoms- no radioactivity
inside bacteria
c. Experiment No.2- Bacteria infected with phages
with radioactive phosphorus atomsradioactivity found inside bacteria
d. Concluded phages
DNA had entered bacteria
but proteins had not.
Genetic material must
be DNA
II. Structure of DNA (8.2)
A. DNA is composed of four types of
nucleotides
1. DNA is long
polymer composed
of monomers called
nucleotides.
a. Each nucleotide has three parts
1). Phosphate group
2). Ring-shaped sugar called deoxyribose
3). Nitrogen-containing base
b. Scientists first believed that DNA was made of
equal parts of four different nucleotides (same in all
organisms
2. In 1950 Erwin Chargaff changed thinking by
analyzing DNA of several different organisms
a. Found same four bases of DNA in all
organisms
b. Proportions of 4 bases were different in
organisms
c. Found amount of adenine equals thymine and
amount of cytosine equals amount of guanine.
A = T and C = G (called Chargaff’s rules)
B. Watson and Crick developed accurate model of
DNA’s three-dimensional structure
1. Used previous work of other scientists and
hypothesized that DNA might also be a
helix
a. Rosalind Franklin and Maurice Wilkins used xray crystallography and suggested DNA helical
shape
b. Work of Hershey, Chase, Chargaff, and Linus
Pauling
2. In 1953 Watson and Crick published their DNA
model in a paper in the journal Nature
a. DNA was double helix
b. Strands are
complementary (they fit
together and are the
opposites of each otherpairing of bases according
to Chargaff’s rules
3. Nucleotides always pair in the same way
a. Backbone formed by covalent bonds that
connect sugar of one nucleotide to phosphate
of another
b. Two sides held
together by weak
hydrogen bonds
between bases
c. Base pairing
rules- A with T and
C with G
III. DNA Replication (8.3)
A. Replication copies the genetic information
1. Replication creates
exact copies of itself
during the cell cycle
2. Replication assures
every cell has complete
set of identical genetic
information
B. Proteins (enzymes) carry out the process of
replication
1. Enzymes begin to unzip double helix
(DNA polymerases)
a. Hydrogen bonds are broken
b. Molecule separates exposing bases
2. Free-floating nucleotides pair up one-by-one
forming complementary strands to template
3. Two identical molecules of DNA formed
C. Replication is fast and accurate
1. Process takes just a few hours
2. DNA replication starts at many points in
eukaryotic chromosomes.
3. DNA polymerases can find and correct errors.
T
A
A
C
A
C
A
G
A
A
T
T
G
T
G
T
C
T
1. First the DNA must unzip:
Enzymes split apart the base pairs
and unwind the DNA.
T
A
A
C
A
C
A
G
A
A
T
T
G
T
G
T
C
T
T
A
A
C
A
C
A
G
A
A
T
T
G
T
G
T
C
T
T
A
A
C
A
C
A
G
A
C
T
T
T
A
T
T
G
T
G
T
2. Bases pair up: Free nucleotides in
the cell find their complementary
bases along the original strand.
T
A
A
C
A
C
A
G
A
T
A
C
T
A
T
T
G
T
G
T
C
T
T
A
A
C
A
A
T
T
G
A
G
A
C
T
C
T
T
A
T
C
A
T
G
T
T
A
A
C
A
C
A
G
A
T
C
T
T
C
T
C
G
T
A
A
A
T
T
G
T
G
3. Backbone Bonds: The sugarphosphate backbone is assembled to
complete the DNA strand
T
A
A
C
A
C
A
G
A
T
G
T
G
T
C
T
C
T
G
T
T
A
A
C
A
C
A
A
T
T
G
T
G
T
T
A
A
C
A
C
A
G
A
T
T
G
T
G
T
C
T
A
A
T
A
A
C
A
C
A
G
A
T
T
G
T
G
T
C
T
T
A
A
C
A
C
A
G
A
A
T
T
G
T
G
T
C
T
T
A
A
C
A
C
A
G
A
A
T
T
G
T
G
T
C
T
The DNA is now duplicated:
The cell can now divide into two
daughter cells.
IV. Transcription (8.4)
A. RNA carries DNA’s instruction
1. Francis Crick defined the central
dogma of molecular biology
a. Replication copies DNA
b. Transcription converts DNA
message into intermediate
molecule, called RNA
c. Translation interprets an
RNA message into string of
amino acids, called
polypeptide (protein)
2. In prokaryotic cells processes take place in
cytoplasm
3. In eukaryotic cells processes are separated
a. Replication and Transcription in nucleus
b. Translation occurs in cytoplasm
4. RNA acts as messenger between nucleus and
protein synthesis in cytoplasm
5. RNA differs from DNA in three significant ways
a. Sugar in RNA is ribose not deoxyribose
b. RNA has the base uracil in place of
thymine
c. RNA is single stranded not double
B. Transcription makes three types of RNA
1. Transcription copies sequence of DNA
(one gene) and is catalyzed by RNA
polymerases
a. DNA begins to unwind at specific site
(gene)
b. Using one strand of DNA, complementary
strand of RNA is produced
c. RNA strand detaches and DNA reconnects
2. Transcription produces 3 kinds of RNA
a. Messenger RNA (mRNA)- code for
translation
b. Ribosomal RNA (rRNA)- forms part of
ribosome
c. Transfer RNA (tRNA)- brings amino acids
from the cytoplasm to a ribosome to help
make growing protein
3. The transcription process is similar to replication
a. Both occur in nucleus
b. Both involve unwinding of DNA
c. Both involve complementary base pairing
V. Translation (8.5)
A. Amino acids are coded by mRNA base
sequences
1. Translation converts mRNA
messages into polypeptides
2. A codon is a sequence of three
nucleotides that codes for an amino
acid.
a. RNA could code 64 different combinations
b. Plenty to cover the 20 amino acids used to build
proteins in human body and most other organisms
c. Many amino acids coded by more than one
codon
d. Also special codons
1). Start codon- signals start of translation
2). Stop codon- signals end of amino acid
chain
3. This code is universal- same in almost all
organisms
a. Suggests
common ancestor
b. Means scientist
can insert gene from
one organism into
another to make
functional protein
B. Amino acids are linked to become a protein
1. Two important “tools” needed to translate a
codon into an amino acid
a. Ribosome- site of protein synthesis
b. tRNA- carries free-floating amino acids from
cytoplasm to ribosome
1). tRNA attaches to specific amino acid
2). Has “3-letter” anticodon that recognizes
a specific condon
2. Translation occurs in cytoplasm of cell
a. mRNA binds to ribosome
b. Ribosome pulls mRNA strand through one
codon at a time
c. Exposed codon attracts complementary tRNA
bearing an amino acid
anticodon
codon
d. Amino acids bond together and tRNA molecule
leaves to find another amino acid
e. Ribosome moves down mRNA attaching more
amino acids until reaches stop codon.
Protein molecule
stop codon
VI. Gene Expression and Regulation (8.6)
A. Your cells can control when gene is “turned
on or off”
B. Different in prokaryotic and eukaryotic cells
C. Because cells are specialized in
multicellular organisms, only certain genes
are expressed in each type of cell.
VII. Mutations (8.7)
A. Some mutations affect a single gene,
while others affect an entire chromosome
1. Mutation- a change in an organism’s
DNA
2. Mutations that affect a
single gene usually happen
during replication
3. Mutations that affect
group of genes or
chromosome happen
during meiosis
B. Gene Mutations
1. Point mutation- one
nucleotide is substituted
for another
Result of simple
point mutation
2. Frameshift mutation- involves insertion or
deletion of a nucleotide in DNA sequence
3. Chromosomal mutationsa. Gene duplication-exchange of DNA
segments through crossing over during
meiosis
b. Gene translocation- results from the
exchange of DNA segments between
nonhomologous chromosomes
C. Mutations may or may not affect phenotype
1. Impact on phenotype-
on
a. Chromosomal mutations affect
many genes and have big affect
organism
b. Some gene mutations change phenotype.
1. A mutation may cause a premature stop
codon.
2. A mutation may change protein shape
or the active site
3. A mutation may change gene regulation
c. Some gene mutations do not affect phenotype
1. A mutation may be silent
2. A mutation may occur in a noncoding
region
3. A mutation may not affect protein folding
or the active site.
2. Mutations in body cells do not affect offspring.
3. Mutations in sex cells can be harmful or
beneficial to offspring
4. Natural selection
often removes mutant
alleles from a population
when they are less
adaptive.
D. Mutations can be caused by several factors
1. Replication errors can
cause mutations
2. Mutagens, such as UV
ray and chemicals, can
cause mutations
3. Some cancer drugs
use mutagenic
properties to kill cancer
cells.
Chapter 8
From DNA to
Proteins
The figure below shows the structure of a(an)
a.
DNA molecule.
b.
amino acid.
c.
RNA molecule.
d.
protein.
The figure below shows the structure of a(an)
a.
DNA molecule.
b.
amino acid.
c.
RNA molecule.
d.
protein.
Identify structure outlined and labeled by the
letter X in Figure below.
a.
RNA
b.
Phosphate
c.
Nucleotide
d.
5-carbon sugar
Identify structure outlined and labeled by the
letter X in Figure below.
a.
RNA
b.
Phosphate
c.
Nucleotide
d.
5-carbon sugar
Which of the following is a nucleotide found in
DNA?
a.
ribose + phosphate group + thymine
b.
ribose + phosphate group + uracil
c.
deoxyribose + phosphate group + uracil
d.
deoxyribose + phosphate group + cytosine
Which of the following is a nucleotide found in
DNA?
a.
ribose + phosphate group + thymine
b.
ribose + phosphate group + uracil
c.
deoxyribose + phosphate group + uracil
d.
deoxyribose + phosphate group +
cytosine
Because of base pairing in DNA, the percentage
of
a.
adenine molecules in DNA is about equal
to the percentage of guanine molecules.
b.
pyrimidines in DNA is about equal to the
percentage of purines.
c.
purines in DNA is much greater than the
percentage of pyrimidines.
d.
cytosine molecules in DNA is much greater
than the percentage of guanine molecules.
Because of base pairing in DNA, the percentage
of
a.
adenine molecules in DNA is about equal
to the percentage of guanine molecules.
b.
pyrimidines in DNA is about equal to
the percentage of purines.
c.
purines in DNA is much greater than the
percentage of pyrimidines.
d.
cytosine molecules in DNA is much
greater than the percentage of guanine
molecules.
DNA is copied during a process called
a.
replication.
b.
translation.
c.
transcription.
d.
transformation.
DNA is copied during a process called
a.
replication.
b.
translation.
c.
transcription.
d.
transformation.
DNA replication results in two DNA molecules,
a.
each with two new strands.
b.
one with two new strands and the other
with two original strands.
c.
each with one new strand and one
original strand.
d.
each with two original strands.
DNA replication results in two DNA molecules,
a.
each with two new strands.
b.
one with two new strands and the other
with two original strands.
c.
each with one new strand and one
original strand.
d.
each with two original strands.
During DNA replication, a DNA strand that has
the bases CTAGGT produces a strand with the
bases
a.
TCGAAC.
b.
GATCCA.
c.
AGCTTG.
d.
GAUCCA.
During DNA replication, a DNA strand that has
the bases CTAGGT produces a strand with the
bases
a.
TCGAAC.
b.
GATCCA.
c.
AGCTTG.
d.
GAUCCA.
In eukaryotes, DNA
a.
is located in the nucleus.
b.
floats freely in the cytoplasm.
c.
is located in the ribosomes.
d.
is circular.
In eukaryotes, DNA
a.
is located in the nucleus.
b.
floats freely in the cytoplasm.
c.
is located in the ribosomes.
d.
is circular.
RNA contains the sugar
a.
ribose.
b.
deoxyribose.
c.
glucose.
d.
lactose.
RNA contains the sugar
a.
ribose.
b.
deoxyribose.
c.
glucose.
d.
lactose.
Unlike DNA, RNA contains
a.
adenine.
b.
uracil.
c.
phosphate groups.
d.
thymine.
Unlike DNA, RNA contains
a.
adenine.
b.
uracil.
c.
phosphate groups.
d.
thymine.
Which of the following are found in both DNA
and RNA?
a.
ribose, phosphate groups, and adenine
b.
deoxyribose, phosphate groups, and
guanine
c.
phosphate groups, guanine, and cytosine
d.
phosphate groups, guanine, and thymine
Which of the following are found in both DNA
and RNA?
a.
ribose, phosphate groups, and adenine
b.
deoxyribose, phosphate groups, and
guanine
c.
phosphate groups, guanine, and
cytosine
d.
phosphate groups, guanine, and thymine
How many main types of RNA are there?
a.
1
b.
3
c.
hundreds
d.
thousands
How many main types of RNA are there?
a.
1
b.
3
c.
hundreds
d.
thousands
Which type(s) of RNA is(are) involved in protein
synthesis?
a.
transfer RNA only
b.
messenger RNA only
c.
ribosomal RNA and transfer RNA only
d.
messenger RNA, ribosomal RNA, and transfe
RNA
Which type(s) of RNA is(are) involved in protein
synthesis?
a.
transfer RNA only
b.
messenger RNA only
c.
ribosomal RNA and transfer RNA only
d.
messenger RNA, ribosomal RNA, and
transfer RNA
What is produced during transcription?
a.
RNA molecules
b.
DNA molecules
c.
RNA polymerase
d.
proteins
What is produced during transcription?
a.
RNA molecules
b.
DNA molecules
c.
RNA polymerase
d.
proteins
What does the figure below show?
a.
anticodons
b.
the order in which
amino acids are linked
c.
the code for
splicing mRNA
d.
the genetic code
What does the figure below show?
a.
anticodons
b.
the order in which
amino acids are linked
c.
the code for
splicing mRNA
d.
the genetic code
How many codons are needed to specify three
amino acids?
a.
3
b.
6
c.
9
d.
12
How many codons are needed to specify three
amino acids?
a.
3
b.
6
c.
9
d.
12
What happens during the process of translation?
a.
Messenger RNA is made from DNA.
b.
The cell uses information from messenger
RNA to produce proteins.
c.
Transfer RNA is made from messenger
RNA.
d.
Copies of DNA molecules are made.
What happens during the process of translation?
a.
Messenger RNA is made from DNA.
b.
The cell uses information from
messenger RNA to produce proteins.
c.
Transfer RNA is made from messenger
RNA.
d.
Copies of DNA molecules are made.
Genes contain instructions for assembling
a.
purines.
b.
nucleosomes.
c.
proteins.
d.
pyrimidines.
Genes contain instructions for assembling
a.
purines.
b.
nucleosomes.
c.
proteins.
d.
pyrimidines.
Which type of RNA functions as a blueprint of
the genetic code?
a.
rRNA
b.
tRNA
c.
mRNA
d.
RNA polymerase
Which type of RNA functions as a blueprint of
the genetic code?
a.
rRNA
b.
tRNA
c.
mRNA
d.
RNA polymerase
A mutation that involves a single nucleotide is
called a(an)
a.
chromosomal mutation.
b.
inversion.
c.
point mutation.
d.
translocation.
A mutation that involves a single nucleotide is
called a(an)
a.
chromosomal mutation.
b.
inversion.
c.
point mutation.
d.
translocation.
Completion:
The Watson and Crick model of DNA is a(an)
__________ ____________, in which two strands
are wound around each other.
Double Helix
Completion:
The figure below shows three types of
____________.
RNA molecules
Completion:
During transcription, the ___________________
between base pairs are broken.
Hydrogen bonds
Completion:
The order of nitrogenous bases in DNA determines
the order of ____________________ in proteins.
Amino acids
Completion:
The ____________________ of a tRNA molecule
determines the type of amino acid that bonds with
the tRNA.
anticodon
What is the name of the yellow structure that is
“landing” onto the blue structure?
bacteriophage
What process is taking place below?
Translation
Mutations seen below are caused by genes
known as _____ genes.
hox
These scientists discovered the structure of a
DNA molecule. Who are they?
Watson and Crick
Which type of RNA below is involved with the
process of translation?
All three
What process is diagramed below?
transcription
What is this structure?
Nuclear envelope
Sickle cell anemia is caused by what type of
genetic mutation?
Point mutation